Device for spraying dry ice, particularly frozen carbon dioxide, and nozzle for said device

ABSTRACT

The invention concerns a device for spraying particles of dry ice, in particular for cleaning surfaces, comprising a gun ( 10 ) for orienting a drive fluid entraining said particles in a first direction, and a spray nozzle ( 4 ) for passage of said drive fluid loaded with said particles, said nozzle ( 4 ) comprising a neck ( 6 ). According to the invention, said device is configured so as to orient the fluid loaded with said particles in at least one other direction upstream of the neck ( 6 ) in the direction of flow of the drive fluid.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a 371 of International Application PCT/FR2012/051870 filed Aug. 8, 2012, which claims priority to French Application No. 1158105 filed Sep. 13, 2011, the entire contents of which are incorporated herein by reference.

BACKGROUND

The present invention concerns a device for spraying dry ice, in particular carbon dioxide ice, and a nozzle for such a device.

It will find its applications, in particular, in the field of cleaning surfaces, in particular large surfaces such as vehicle bodywork parts. This example is however not limitative and the invention will also find its applications in particular for cleaning smaller parts.

Cleaning by spraying carbon dioxide ice finds its efficacy in the combination of various effects, a mechanical effect due to the kinetic energy of the particles of ice, a thermal effect due to the temperature of the particles and a blowing effect due to the sublimation of the ice in contact with the surface to be cleaned. It also has the advantage of not leaving residues. This is because, after sublimation, the carbon dioxide ice, transformed into gas, discharges by itself.

Various methods for cleaning by spraying carbon dioxide ice have already been proposed. Spraying particles or pellets of ice previously formed by means of a firing machine is thus known. This method may however prove to be too violent for fragile surfaces.

Forming particles of ice from carbon dioxide in the liquid state in contact with a drive fluid that drives the particles as they are created and also serves to spray them onto the surface to be cleaned is also known.

In order to implement this last method, devices are known comprising a supply of driving fluid, a supply of liquid carbon dioxide, a chamber for forming particles of carbon dioxide ice and a nozzle spraying, under the action of the drive fluid, the particles formed in the chamber. Such a device is described in the document EP-1765551.

The document DE-102005021999 also illustrates this prior art of such spraying devices.

Such devices are particularly suited to spraying the flow of ice particles in a direction orthogonal to the surface to be cleaned. Difficulties are presented when it is wished to spray the fluid in an inclined direction, in particular in the case of a surface to be cleaned having a complex profile.

A first solution for solving this problem would be to incline the device in a required direction but, because of the bulk thereof, this would pose problems of protuberance.

Another solution would be to orient the flow at the discharge from the nozzle but this would create pressure drops which would greatly degrade the performance of the cleaning. This is because the flow of ice particles, greatly accelerated after passage through the nozzle, is particularly sensitive to any disturbances.

SUMMARY

The invention aims to improve the situation and for this purpose proposes a device for spraying particles of dry ice, in particular for cleaning surfaces, comprising a gun for orienting a drive fluid entraining said particles in a first direction, and a spray nozzle enabling said drive fluid to pass, loaded with said particles, said nozzle comprising a neck.

According to the invention, said devices configured so as to orient the fluid, loaded with said particles, in at least one other direction upstream of the neck, in the direction of flow of said drive fluid. A solution is thus available for orienting the flow of particles in the desired direction while limiting the pressure drops.

To avoid any doubt, hereinafter the term “cross-section” means the cross-section of the nozzle in a plane orthogonal to the principal direction in which the nozzle conducts the fluid passing through it.

According to various embodiments of the invention that can be taken together or separately:

-   -   the nozzle comprises a convergent device intended to be situated         upstream of the neck in the direction of flow of the drive         fluid, and said device is configured so as to orient the fluid         in said other direction or directions upstream of said         convergent device,     -   the nozzle comprises a portion with a constant cross-section         intended to be situated upstream of the convergent device in the         direction of flow of the drive fluid, and said device is         configured so as to orient the fluid in said other direction or         directions upstream of said portion of constant cross-section,     -   said device comprises a passage elbow connecting the gun and the         nozzle, said elbow being able to divert said drive fluid, loaded         with said particles, from said first direction into said other         direction or directions,     -   the nozzle is configured so as to divert the drive fluid, loaded         with said particles, in the other direction or directions,     -   the nozzle comprises a diversion portion, able to modify the         path of said drive fluid, loaded with said particles, from said         first direction into said other direction or directions, said         diversion portion being situated upstream of the neck,     -   the nozzle comprises a convergent device and said diversion         portion is situated at least partly level with said convergent         device,     -   the nozzle comprises a portion of constant cross-section         intended to be situated upstream of the convergent device in the         direction of flow of the drive fluid, said portion of constant         cross-section being able to guide the drive fluid, loaded with         said particles, in said first direction.

According to one aspect of the invention, said nozzle comprises a divergent nozzle enabling an acceleration of said drive fluid in said other direction or directions.

Said divergent nozzle extends between the neck and a discharge orifice of the nozzle, the ratio between the surface area of the neck and the surface area of said discharge orifice of the nozzle being, for example, greater than 0.2, in particular greater than 0.5, especially greater than 0.73. Said ratio will for example be less than 0.9.

The applicant in fact found, following numerous tests, that such a divergent nozzle made it possible to limit the consumption of carrier fluid while obtaining very good cleaning results, in particular in terms of eliminating fatty imprints present on the objects to be cleaned. The invention will more generally find its applications for cleaning fine pollutions, with a thickness of less than 3 mm, among other things. It also makes it possible to use nozzles of limited size, in particular nozzles having divergent nozzles where the length between the neck and the discharge orifice of the nozzle is less than 50 mm.

According to a first embodiment, said divergent nozzle has a rectangular cross-section.

According to various aspects of this first embodiment, which can be taken together or separately:

-   -   the length I of said cross-section increases in a linear fashion         going from the neck towards the discharge orifice of the nozzle,     -   said cross-section has a substantially constant width or height,         going from the neck towards the discharge orifice of the nozzle,     -   the discharge orifice of the nozzle is in the form of a slot         having a width or height of less than 1.5 mm and/or a length         between 20 and 50 mm,     -   the neck has a rectangular cross-section.

According to another embodiment of the invention, said divergent nozzle has a circular cross-section. The neck can then have a circular cross-section.

To avoid any doubt, the term “angle of divergence” will hereinafter have the following meaning. For nozzles where the divergent nozzle has a rectangular cross-section in which the length I increases linearly, it is the angle corresponding to the slope of increase of said length I of the divergent nozzle. For nozzles where the divergent nozzle has a round cross-section, it is the angle at the vertex of the cone carrying the truncated cone forming the divergent nozzle.

According to a first variant, the divergent nozzle of the device according to the invention has an angle of divergence a of around 6°. Great cleaning efficiency is then obtained.

According to a second variant, said divergent nozzle has an angle of divergence a greater than 7°, in particular greater than 15°. A splayed jet with an enlarged impact surface is then obtained.

In these various variants, the length L of the divergent nozzle measured between the neck and the discharge orifice of the nozzle, the length I_(S) of the cross-section of the divergent nozzle at said discharge of the nozzle and the angle of divergence a follow the following law:

(0.05×I _(S))/tan (α)≦L≦(0.4×I _(S))/tan (α).

According to one aspect of the invention, said neck is a sonic neck. The convergent device and divergent nozzle are for example directly connected to each other at the neck.

According to a variant, the discharge orifice of the nozzle is level with the neck. Such a nozzle has cleaning performances lower than the previous ones but remains of interest in that it also affords a reduction in the consumption of carrier fluid.

The invention also concerns a nozzle of a spray device as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates schematically an example of a spray device according to the invention, partially cut along a longitudinal cutting plane,

FIG. 2 illustrates schematically another example of a spray device according the invention,

FIG. 3 illustrates, in a view in longitudinal section, a nozzle of a device according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

As illustrated in FIGS. 1 and 2, the invention concerns a device for spraying particles of dry ice, for example carbon dioxide ice, in particular for cleaning surfaces.

Said device comprises a gun 10 for orienting a drive fluid entraining said particles in a first direction, marked D1, and a spray nozzle 4, enabling said drive fluid to pass, loaded with said particles. Said drive fluid is for example compressed air.

The gun 10 is provided in particular with a supply 1 of drive fluid, a supply 2 of liquid carbon dioxide and a chamber 3 for forming particles of carbon dioxide ice (not illustrated in FIG. 2). The nozzle 4 is connected to the gun 10 and, under the action of the drive fluid, sprays the particles formed in the chamber 3.

In more detail, according to such an example embodiment, the drive fluid enters the device through the drive-fluid supply 1 and is then loaded with particles of ice generated in the chamber 3, at the discharge of said chamber. In this way a flow is formed of drive fluid and ice particles that passes through the nozzle 4 in order to be sprayed onto the part to be cleaned.

According to the invention, said device is configured so as to orient the fluid, loaded with said particles, in at least one other direction, marked D2, upstream of the neck 6 of the nozzle 4, in the direction of flow of the drive fluid. In this way a diversion of the flow of particles is obtained while limiting the pressure drops. By way of example, the angle between said first direction D1 and said other direction D2 is approximately 45°.

As illustrated in the variant in FIG. 1, the nozzle 4 may comprise a convergent device 8, intended to be situated upstream of the neck 6 in the direction of flow of the drive fluid, and said device is configured so as to orient the fluid in the direction D2 upstream of said convergent device 8.

In this variant, the nozzle 4 also comprises a portion 20 with a constant cross-section, intended to be situated upstream of the convergent device 8 in the direction of flow of the drive fluid, and said device is configured so as to orient the fluid in the direction D2 upstream of said constant cross-section 20.

Still in this variant, said device comprises a passage elbow 21 connecting the gun 10 and nozzle 4, said elbow 21 being able to divert said drive fluid loaded with said particles, from said first direction D1 into the direction D2. Said elbow 21 has in particular a tubular cross-section. It is a separate part attached between the gun 10 and the nozzle 4. Such an embodiment makes it possible to have available identical nozzles for spraying with or without diversion of the jet of particles, depending on whether or not the nozzle 4 is connected to the gun 10 by means of the elbow 21.

Said nozzle 4 and the gun 10 can have complementary fixing means, not illustrated, and the elbow 21 may comprise fixing means of an identical nature, not illustrated, enabling it to cooperate with the fixing means of the gun 10 and nozzle 4. “Of identical nature” means fixing means not requiring an adaptor to enable the parts to be connected together.

As illustrated in FIGS. 2 and 3, according to other preferred variants according to the invention, it is the nozzle 4 that is configured to divert the drive fluid loaded with said particles in the direction D2.

For this purpose, the nozzle 4 may comprise a diversion portion 22 able to modify the path of said drive fluid loaded with said particles from said first direction D1 into the direction D2, said diversion portion 22 being situated upstream of the neck 6.

The nozzle 4 comprises for example a convergent device 8 and said diversion portion 22 is situated level with said convergent device 8.

The nozzle 4 comprises, for example, a portion 23 with a constant cross-section, intended to be situated upstream of the convergent device 8 in the direction of flow of the drive fluid, said portion 23 of constant cross-section being able to guide the drive fluid loaded with said particles in said first direction D1.

Said portion 23 with a constant cross-section is here connected to the convergent device by a plane 24, inclined with respect to the direction D1 and orthogonal to the direction D2. The part of the nozzle 4 situated downstream forms an acceleration portion.

This being the case, according to a variant that is not illustrated, the nozzle may comprise an angled part upstream of its convergent device, or even upstream of a portion of constant cross-section of the nozzle, connected to said convergent device.

As illustrated in the various figures, according to an advantageous embodiment of the invention, said nozzle 4 comprises a divergent nozzle 7 for accelerating said drive fluid in the direction D2.

Said divergent nozzle 7 extends, for example, between the neck 6 and a discharge orifice of the nozzle 5. The neck 6 and said discharge 5 of the nozzle 4 are for example orthogonal to the direction of the drive fluid loaded with said particles.

The ratio between the surface area of the neck 6 and the surface area of said discharge orifice 5 of the nozzle is for example greater than 0.2, especially 0.5, in particular 0.73. It will for example be less than 0.9. The applicant has in fact found that such a choice of size affords suitable acceleration of the particles with reduced consumption of drive fluid. Said surface ratio may for example be between 0.8 and 0.9.

Said divergent nozzle 7 has for example a rectangular cross-section. The length I of said cross-section increases linearly and has a substantially constant width and height, going from the neck 6 towards the discharge orifice 5 of the nozzle 4. It is a case in particular of a width or height configured to the size of the particles formed. It will thus be possible to use a width or height of less than 2 mm, for example around 1.2 or 1.3 mm.

The neck 6 has here a rectangular cross-section, one of the dimensions of which corresponds to the width or height of the divergent nozzle 7.

Said divergent nozzle has moreover an angle of divergence a of approximately 6° making it possible to preserve a substantially straight flow at the discharge from the nozzle. In a variant, it may be an angle greater than 7°, for obtaining a broadening of the flow as a discharge from the nozzle.

More precisely, said divergent nozzle 7 may have a length L of said nozzle 4, measured between the neck 6 and the discharge orifice 5 of said nozzle 4, a length I_(s) of the cross-section of the divergent nozzle at said discharge 5 of the nozzle and an angle of divergence a in accordance with the following law:

(0.05×I _(S))/tan (α)≦L≦(0.4×I _(S))/tan (α).

In particular, L may have as its upper limit: (0.1×I_(S)) / tan (α).

The discharge orifice 5 of the nozzle is in the form of a slot. This may have a height of less than 2 mm, in particular around 1.2 or 1.3 mm, and/or a length of between 10 and 50 mm, in particular between 20 and 50 mm.

According to another example embodiment that is not illustrated, said divergent nozzle has a circular cross-section. In other words, the divergent nozzle is frustoconical in shape. Said neck can then have a circular cross-section. The angle of divergence may be around 6° or greater than 7°, with the same effects as those described above. The convergent device will then also be circular and the angled portion in accordance with the information will be either at the nozzle, upstream of the neck, or upstream of said nozzle.

By way of example, the divergent nozzles 7 of the nozzles 4 according to the invention have a length, measured between the neck and the discharge orifice of the nozzle, of less than 200 mm, in particular 50 mm. It may in particular be a length less than 10 mm for nozzles having an angle of divergence greater than 7°.

In FIGS. 2 and 3, the convergent device 8 and the divergent nozzle 7 are connected directly to each other at the neck 6. In other words, the neck 6 is a simple plane. In a variant, as illustrated in FIG. 1, the neck 6 may have a non-zero length.

In another variant that is not illustrated, the nozzle does not comprise a divergent nozzle. Its discharge orifice is therefore situated at its neck. The acceleration obtained will thus be limited to that offered by the sonic neck, which may however suffice and even be more favourable, in particular for cleaning surfaces that are not very dirty and/or are particularly fragile.

This being the case, said neck 6 is a sonic neck and an absolute pressure of between for example 4 and 16 bar, in particular 4 and 6 bar, will be provided at the inlet of the nozzle 4. Said nozzle comprises, for example, a body 30 defining said convergent device 7, said neck 6 and/or said divergent nozzle 8, said body optionally being angled.

It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above. 

1.-2. (canceled)
 3. A device for spraying particles of dry ice, comprising a gun for orienting a drive fluid entraining said particles in a first direction, and a spray nozzle for passage of said drive fluid loaded with said particles, said nozzle comprising a neck, wherein said device is configured to orient said drive fluid loaded with said particles in at least one other direction upstream of the neck in the direction of flow of the drive fluid, and in that the nozzle is configured to divert the drive fluid loaded with said particles in the other direction or directions, as follows: the nozzle comprises a diversion portion able to modify the path of said drive fluid loaded with said particles, from said first direction into said other direction or directions, said diversion portion being situated upstream of the neck; the nozzle comprises a convergent device wherein said diversion portion is situated at least partly at said convergent device.
 4. The device according to claim 1, in which the nozzle further comprises a portion with a constant cross-section situated upstream of the convergent device in the direction of flow of the drive fluid, said portion with a constant cross-section being able to guide the drive fluid loaded with said particles in said first direction. 